The present invention relates in general to mobile radio communications, and deals more particularly with the art of interfacing a half duplex frequency two-way radio communications system with ordinary land-line telephone networks.
Dedicated mobile telephones systems and remote telephone calling and answering systems are well known. Also known is the use of ordinary two-way mobile radios and an associated base radio station to communicatively link a mobile telephone terminal with land-line telephone exchanges. A system of this type is disclosed in U.S. Pat. No. 3,586,978 to Duyck Van Gorder. However, prior art systems possess several deficiencies which preclude their use in certain applications and impede their effectiveness under some circumstances.
The present invention surmounts these shortcomings, in part through the use of several novel features including dual radio operating frequencies to allow half duplex transmission and reception, and unique circuit means which allow the licensee of the radio communications system to maintain exclusive control of the base station radio.
The subject invention provides for communicatively interfacing a base station radio having separate frequencies for transmission and reception, to ordinary telephone networks. A carrier frequency actuated relay is operated by an incoming signal transmitted from a mobile radio, thereby switching the base station audio as required. Upon decoding, an enabling signal actuates a relay combination to connect incoming telephone lines via an audio coupling transformer to the base station radio, thereby accessing the telephone network to the mobile radio operator. Similarly, the decoding means are responsive to ring signals and enabling signals produced by an incoming telephone call, likewise accessing the mobile radio units to the land-line caller. As an optional feature, circuit means are provided to detect a received ringing signal and function to cause the same to be transmitted to the mobile radio units to alert the mobile personnel of the presence of the incoming call at the base radio station. The decoding means further function to detect a disable signal received from either a mobile radio or a land-line telephone, and operate to unlatch relay combinations which disconnect the audio coupling transformer from the base station radio and telephone lines. A protective timing circuit is operative to likewise effect this disconnection after a preselected elapsed time following the last detected communication.
A primary object of the invention is to provide a unique method and electronic control device for radio telephone communication.
Another object of the invention is to provide a unique method and electronic control device for communicatively interfacing a half duplexed frequency radio communications system with ordinary land-line telephones.
Another object of the invention is to provide a method and electronic control device of the character described wherein the said electronic control device functions to automatically interface a base station radio with an ordinary telephone set.
Another object of the invention is to provide a method and electronic control device of the character described immediately above which includes circuit means that function to automatically connect the associated base station radio with an outgoing telephone line, upon receipt of a coded enabling signal, such that the mobile operator may carry on an ordinary conversation with a land-line party over said telephone line. It is a feature of the invention that the enabling coded signal may be generated either by a mobile radio unit operator or a party having access to a land-line telephone set.
A still further object of the invention is to provide a method and device of the character described allowing the lincensee of the base radio station to maintain exclusive operative control thereof, thereby permitting the legal use of same in connection with business, industrial and public security applications. Known prior art devices, such as mobile telephones do not provide this necessary exclusive control feature and therefore do not conform to the Rules and Regulations of the Federal Communications Commission so as to legalize their use in above-mentioned applications.
Another object of the invention is to provide, in a communication environment of the character described, a unique circuit means and control device to modulate a base station radio transmitter using a distant land-line telephone. Known prior art accomplishes this function through the use of more expensive leased telephone lines or, alternatively, through the use of microwave communication.
A further object of the invention is to provide, in a communication environment of the character described, a unique circuit means and control device to notify a mobile unit operator of an incoming telephone call to the associated base radio station.
Another object of the invention is to provide a method and device of the character described which enables radio communications systems of different operating frequencies to intercommunicate with each other via ordinary dial network telephone lines.
Other and further objects of the invention, together with the features of novelty appurtenant thereto, will appear in the course of the following description.